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What is the dimensional formula of the quantity (1/2)*epsilon0*E², where epsilon0 is the permittivity of free space and E is the electric field strength?

1. M L⁻¹ T⁻²
2. M L² T⁻²
3. M L T⁻²
4. M L² T⁻¹

Correct answer: M L⁻¹ T⁻²

Solution

(1/2)*epsilon0*E² is the electrostatic energy stored per unit volume (energy density). Energy has dimensions M L² T⁻² and volume has L³, so energy density is M L⁻¹ T⁻² (same as pressure).

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